Disc brake pads become contaminated while on turbo

I have a gravel bike that I use on an Elite Direto X. I find that the rear disk brake pads become contaminated while on the turbo. When I ride outside and put the wheel back on, it normally takes a few minutes of hard braking to stop the squeal and return the brake to full power.

I don’t use any sprays or anything that would normally cause this kind of problem.
Is it simply the air coming in contact with the pad because it is exposed more?
Has anyone come across this before, or have any suggestions?

Do you use a brake pad spacer while the bike is on the trainer? I imagine that might protect the pad surfaces a bit from whatever contamination you are getting?

(In any case, thank you for providing another anecdote that I can use to justify my irrational stubbornness and stick with rim brakes)


Are they hydraulic brakes? You might be accidentially pulling the brake a bit now and then, and the pistons move out, but without the disc there (it’s a direct drive trainer, right?), they don’t go back to their proper place. Using a spacer should help, or simply pull the brake hard a few times after you put the wheel back in. (Not before!)

This was happening to me and it drove me nuts for a while until I realized that the housekeeping service we use was “cleaning” my bike with some sort of bottled solution.

Not sure if you’re a candidate for this …

I now clean that room myself and keep the door locked whenever they’re here :metal:

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I’ve been using a Direto X for 2 years and haven’t had this issue at all. There’s nothing on the non-drive side that would even contaminate the pads. It’s just a solid plastic casing. Whatever is happening here, it’s not coming from your trainer.

Where do you store your back wheel when your bike is on the trainer? My guess is that it’s your rotor that is actually getting contaminated while off the bike.

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Related question, what is happening with the wheel when it’s not on the bike?

  • It’s possible (and even more likely?) that the issue comes from mishandling or storage of the wheel (and more exposed disc rotor), not the bike.
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Great minds think alike!

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Indeed, duplicate as I missed your reply via writing mine :stuck_out_tongue:

Do you use a brake pad spacer while the bike is on the trainer?

I don’t use a pad spacer, but I am very careful not to pull on the rear brake.

the housekeeping service we use was “cleaning” my bike with some sort of bottled solution.

I unfortunately don’t have a cleaner so thats not the problem.

Where do you store your back wheel when your bike is on the trainer?
My back wheel is stored just next to the bike/turbo against the wall. Why would that cause contamination, but the front wheel which is just next to it (but on the bike) not have any such issues.

Does anyone take the pads out while their bike is on the turbo? Seems like a faff, but might be worth a try. I’ll also try storing my wheel with a rotor cover to see if that helps.

I’m admittedly new to bike disc brakes but I have a ton experience DIYing my car disc brakes and they basically work the same.

  1. Disc brakes self adjust so any time you are removing and replacing the wheel, you are very likely spreading the pads a bit and it takes a few applications of the brakes to get them back in good position. That is just a normal feature of hydraulic disc brakes. This sounds to me what you are experiencing. Just squeeze the brakes a few times right after you put the wheel back on and this should avoid going through that adjustment process while on the road.

  2. As mentioned, if you apply the brakes without the disc in there, the pads will “adjust” themselves to compensate. The gap will get super narrow and you’ll have to manually spread them apart to get the wheel back on. That does not sound like what you are experiencing. Using a spacer whenever you take a wheel off will eliminate the risk of this happening.

  3. If the pads or disc get contaminated that will affect braking but may clear itself up after several applications of the brakes under load (e.g. When your car brake discs get a little rusty after a rain and squeal for the first few stops). That could be happening to you although I think #1 is more likely unless you are really sweating a ton on the bike or spraying sports drink everywhere. There are disc brake spray cleaners you can get that will clean the brake surfaces. There are also car disc brake cleaners that are 1/4th the cost which I assume work the same or better :wink:

Sounds like oil/contamination to me as per:

OP, if you’re washing the bike before riding outside it could well be contamination from any soap etc used. If not, likely something is touching the disc when it’s off the bike. A wheel bag for the wheel and maybe a plastic bag over the caliper just to be sure will eliminate any chance of issues.

Standard car brake maintenance practice is to spray brake cleaner on the disc and pads anytime you touch them or are working around them with anything oily even if you don’t touch the brake parts. In my brief time with bike disc brakes reading maintenance tips, the bike crowd seems less hyper about clean brakes then the car crowd which does not make much sense. Car brakes are rarely called upon for max force (unless its a race car) and the temps car brakes hit even on the street make them kind of self cleaning whereas bike brakes are often operated close to max and seem like they’d be more sensitive to contamination and have less room for degraded performance.

You can also clean the pads to a degree by popping them out and putting them over a gas hob - get them nice and hot until smoking and then allow to cool. Then give them a quick rough with new clean glass paper. Then pop them back in.

As others have said it may be where your rotor is that’s picking stuff up. Try using some car disk brake cleaner on the rotors as per the instructions

Also some fluid can leak around the pistons which may cause issues - :thinking: though not sure how it’d get on the pads as it’d be on the back but could drip down onto the rotor. You say you’re not pulling the brake but only light pressure with no rotor in the way can cause pistons to move in and out beyond their normal point.

Have your brakes always squealed? If not give them a very good looking over. Mine only make noises with contaminated pads and once cleaned/changed and the rotor cleaned its back to peace and quiet :shushing_face:.


Fastest adn easiest way to stop brake squeal…works great and only takes about 5 min / wheel.

I always use a spacer when I put my bike on the trainer. Buy a pad spacer either off eBay/Amazon or see if you can buy one or two from your lbs, they’re a couple of bucks and come in handy when you’re working on the bike with wheels off/cleaning/bleeding brakes. You can use isopropyl alcohol to clean the rotor and the pads if you touch it with bare hands and then just do some progressively harder brake checks before you go out for a ride to be sure everything is working correctly.

My trainer bike does not have brakes, but if it did, I would totally believe it would be contaminated. Just from the build up of gunk on the bike, and the trainer. I even get wax bits from the chain onto the brake side of the trainer body.

Stuff gets everywhere. Ignoring all the cruft on my front wheel and fork, which has it’s own ton of stuff going on there.

Maybe try leaving fans on after the workout? I always forget to turn them off, so I turn it off right after I’m done, and the area is noticeably more humid than other areas.

I use a clean popsicle stick as a spacer, held in place by a rubber band. Wash the stick with soap and water after eating the ice cream, then dry it with a paper towel. The stick is always dirty after using it as a spacer, so I’ve never tried cleaning and re-using it.

How many ice creams (lolly ices)? Do you eat, if you replace the stick everytime?

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